Effects of light intensity and quality on the relative N and P requirement (the optimum N:P ratio) of marine planktonic algae

• Published in: Journal of plankton research 1986, Vol.8 (1), p.91-103
• Main Authors: Wynne, D., Rhee, G-Y.
• Format: Article
• Language: English
• Subjects: Animal and plant ecology; Animal, plant and microbial ecology; Biological and medical sciences; Dunaliella tertiolecta; Fundamental and applied biological sciences. Psychology; Marine; Phaeodactylum tricornutum; Prymnesium parvum; Sea water ecosystems; Synecology; Thalassiosira pseudonana
• ISSN: 0142-7873; 1464-3774
• DOI: 10.1093/plankt/8.1.91

The relative requirement of N and P (the optimum N:P ratio) by Dunaliella tertiolecta, Phaeodactylum tricornutum, Prymnesium parvum and Thalassiosira pseudonana was studied under various light intensities and spectra. The ratio was determined as the ratio of the minimum cell N and P concentrations (q0N and q0p when either nutrient was limiting. The ratio varied widely among species; under light-saturation for growth (116 μEin m−2 s−1 it ranged from 11.8 in D. tertiolecta to 36.6 in P. tricornutum. The ratio appeared to be higher at a sub-saturating intensity (24 μEin m−2 s−1 in all except P. tricornutum, mainly because of higher qoN with little change in qoP. In T. pseudonana QoP also increased, resulting in an insignificant change in the ratio. The ratio varied little within the range of saturation intensity. Light quality affected qoN and qoP as well as the ratio, and the pattern of change varied from species to species. The optimum ratio of individual species was linearly correlated to their qoN except in P. tricornutum. qoN for all species showed a linear correlation with cell protein concentrations irrespective of light conditions. The change of optimum N:P ratios in the three species thus appears to be related to changes in cell protein contents. The ratio of carbohydrates to protein remained constant regardless of light intensity or quality and was higher in P-limited cultures. We conclude that changes in light regime can strongly influence algal nutrient requirements and species interrelationships by altering the optimum cellular N:P ratio.